Influence of Bamboo Powder Incorporation on Carbonation Behavior and Mechanical Performance of Steel Slag-Based Fiberboards

Carbonation curing provides a practical route for improving the performance of steel slag-based materials while enabling CO2 sequestration. In this study, bamboo powder was incorporated into steel slag-based fiberboards at dosages of 0–10 wt.% to investigate its influence on mechanical properties, water absorption, carbonation behavior, phase composition, and microstructure. The results showed that the effect of BP was strongly dependent on its dosage. The water-saturated flexural strength increased with BP content up to 5 wt.% and then decreased at 10 wt.%. After 3 days of carbonation curing, the 5 wt.% BP specimen reached a flexural strength of 23.4 MPa, representing an increase of approximately 88.7% compared with the reference specimen at 12.4 MPa. The same specimen also exhibited the lowest water absorption and the highest CO2 absorption capacity of 15.85 kg CO2/m2, as determined by the loss-on-ignition method. Thermogravimetric analysis showed that the carbonate content reached 29.36% at 5 wt.% BP after 3 days of carbonation curing. XRD and FTIR analyses confirmed that calcite was the dominant carbonation product, while SEM observations showed a relatively compact matrix at moderate BP content. In contrast, excessive BP addition increased structural heterogeneity and weakened the improvement in carbonation and mechanical performance. These results indicate that an appropriate BP content can improve the carbonation response and mechanical performance of SSFB, and 5 wt.% BP was the best-performing dosage within the investigated range.